Wasser im Gartenbau : Tagungsband zum Statusseminar am 9 ... - vTI

Landbauforschung – Sonderheft 328 (2009) 17
Figure 5
Predicted changes in groundwater recharge in case
the actual groundwater recharge rate 1961–1990 is
compared to groundwater recharge rates for the
time period 2071–2099 based on the MM5 data set
as input. The upper part shows the absolute
changes, the lower part the relative changes
According to figure 5 (upper part) for large parts
of the unconsolidated rock areas occurring in
Lower Saxony and North Rhine-Westphalia an
increase of the groundwater recharge rate by
15 mm/a to ca. 35 mm/a to 2100 is predicted.
There the groundwater table might rise in the
coming years. For large parts of the consolidated
rock areas, a decline of up to ca. 15 % was calculated.
Referring these values to the mean
long-term change in the two Federal States this
corresponds to an increase of groundwater recharge
in Lower Saxony by 17 % and by less
than 5 % in North Rhine-Westphalia. It has to be
taken into account that these values are strongly
influenced by the compensation of areas indicating
a net increase with areas indicating a net decline.
The fact that in North Rhine-Westphalia the
portion of areas indicating a decline or an in-
crease of groundwater recharge values are almost
equally shared indicates a relative low
change “on average”.
The relative change (see figure 5, lower part)
conveys an additional effect. Especially along the
coast line of the North see, the increase of
groundwater recharge corresponds to more than
25 % of the groundwater recharge rate calculated
for the period 1960–1989. This might have
some impacts on the regional groundwater management,
e.g. the drainage discharge and ecological
status of the related wetlands. In case the
decrease by 25 % calculated for the southwestern
part of North Rhine-Westphalia would
come true, an impact on the drinking water dams
of the Eifel region would be the consequence.
6.3 Predicted groundwater recharge rates
for the period 2071–2099 in groundwater
resources management related reference
areas
According to annex V of EU WFD the „good
quantitative status“ of groundwater is achieved in
case the mean long-term groundwater extraction
doesn’t exceed the mean long-term groundwater
recharge (sustainable use of groundwater).
Whereas river basin districts provide the basis
for the overall regional water resources management,
groundwater bodies are the geographic
units for regional groundwater resources
management within the river basin districts according
to EU WFD article 4, paragraph 1 b i and
ii. For the Federal States of North Rhine-Westphalia
and Lower Saxony 268 respectively 129
groundwater bodies have been delineated in the
framework of the of river basin characterisation
(2005) according to the groundwater flow conditions.
As the EU WFD requires an integrated
consideration of surface waters and surface near
groundwater occurrences this delineation took
the hydrological water sheds into account too.
Figure 6 shows the expected change in the
mean long-term groundwater recharge for the
period 1961–1990 compared to the groundwater
recharge for the period 2071–2100 related to the
397 groundwater bodies delineated for the two
Federal States.